Control of liquid ink conductivity is important to color consistency within the field of liquid electrophotographic printing (LEP). Toward that goal, a conductivity sensor is needed that can detect variations in the ink's electrical charge during the process of forming an image on media. One approach to measuring LEP ink conductivity is to use two electrodes that are separated, or gapped, by several hundred microns. A voltage of dozens to hundreds of volts is applied and the resulting electrical current between the electrodes is measured and used to determine the electrical conductivity of the ink.
An undesirable aspect of using a high-voltage electric field is that ink “sludge” tends to form on the electrodes. This sludge acts to disrupt or skew subsequent conductivity measurements, with increasing error in the readings as the sludge accumulates. Thus, some means of cleaning is required in order to prevent ink sludge accumulation on electrode surfaces. Furthermore, a fresh supply of the liquid ink must be provided to the electrode surfaces in order to ensure meaningful ink conductivity readings.
Accordingly, the embodiments described hereinafter were developed in light of these and other drawbacks associated with LEP ink conductivity measurements.